Liquid treating apparatus and process



May 30, 1950 w. H. GREEN I 2,509,683

LIQUID TREATING APPARATUS AND PROCESS Filed March 16, 1946 3Sheets-Sheet 1 INVENTOR.

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May 30, 1950 w. H. GREEN 2,509,633

uqum TREATING APPARATUS AND PROCESS Filed March 16, 1946 3 Sheets-Sheet2 INVEN TOR.

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LIQUID TREATING APPARATUS AND PROCESS Filed March 16, 1946 3Sheets-Sheet 3 Q n w & Q

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, been heretofore practically restricted to either Patented May 30, 1950LIQUID TREATING APPARATUS AND PROCESS Walter H. Green, Baum, m, assignorto Iniilco Incorporated, Chicago, 11]., a corporation of DelawareApplication March 16, 1946, Serial No. 654,861

13 Claims.

This invention relates to an apparatus and method for treating liquid bywhat is known as the "slurry process.

One object of my invention is to provide an apparatus in which, and aprocess by which, the available space of the treating tank is more fullyand more efliciently utilized; and in this con- A further object of thisinvention is to provide in a slurry treating apparatus and process, andparticularly one adapted for an elongated basin, a means for accuratecontrol of'flow into the quiescent clarification zone, and the relativevolumes of such flow to circulation in the mixing chamber.

A still further object of my invention is to provide a slurry treatingprocess and apparatus wherein the relative volumes of the flows from themixing zone to the clarification zone and the recirculation within themixing zone may be con trolled separately, with the result thatoperating results can also be controlled. A principal application of myinvention is concerned with the treatment of water, such as softening orclarifying, in a relatively long or a relatively shallow tank.

Apparatus of the type sold under the trade name Accelator, has foundwide acceptance in industrial and municipal treatment of water However,such apparatus has round or square treating basins, and also requiredbasins having considerable depth. I have discovered that the processcarried out in such equipment can be readily used in relatively long,rectangular basins, or in rather shallow basins, and in this respect my"invention is an improvement on such apparatus and process. I am enabledto secure very satisfactory results in what heretofore was considered anunsatisfactory size or shape of a treating basin, or to improve resultsin the usual round basin, by interposing what might be called a pressurechamber between the primary mixing zone and the flow passage discharginginto the quiescent part of the basin, and returning part of the liquidfrom the pressure chamber to the mixing zone.

The Accelator apparatus, as usually constructed, consists essentially ofa sloping wall structure forming a hood in the lower portion of thetreating tank, a flow passage leading from the top of the hood anddischarging downwardly over the hood, and one or more impellers soconstructed and positioned as to cause a circulation of liquid under thehood and a circulation from the top of the hood through the passagewayand over the hoodthe latter circulation being considerably in excess ofthe throughput of the basin. The hood is so designed that its capacityis several times the maximum inflow in gallon per minute, so that whenthe plant is in operation the slurry, the water to be treated and thechemical reagents are mixed and circulated for a period of severalminutes under the hood, then how through the flow passage, down over thetop of the hood and back under the hood-an output quantity rising astreated and fully clarified liquid from the slurry outside the hood.

I have found that two factors which have heretofore been overlooked areimportant in determining the efliciency of the Accelator type apparatus:(a) the velocity and turbulence of the flow through the passageway,particularly as it is discharged out over the top of the hood and (b)the relative volume and velocities of flows under the hood and throughthe passageway. Thus I have found that some Accelators did not give.maximum emciency because the impeller caused either a too turbulentflow through the passageway and out over the hood, or passed too muchover the hood and'failed to provide suficient agitation under it. Itwill be remembered that in apparatus of this type, in which. the entirereaction is compressed into a relatively short period, changes in thecharacter of the water may necessitate considerable change invelocities, relative volumes of flow, and the like. I have found that ifa chamber, which can most descriptively be called a pressure chamber, isinterposed between the hood and the flow passage, and is provided withvalved openings leading into the flow passage and also back under thehood, I can control such factors and can secure much more efilcient anduniform results from this type of apparatus, as in this way the flows orvelocities in the separate passageways and spaces can be regulatedindependently.

It has also been generally accepted that equipment of the Accelator typecould be operated most efiiciently in round and relatively deep tanks.When the principle was applied to a rectangular tank, or to one ofunusually shallow depth in relation to diameter, constructiondifficulties are experienced and the overall efficiency is reduced.

3 I have found that this difllculty was due to the fact that in theusual slurry type apparatus, and particularly those in oblong basins,flows were not uniform in all parts of the apparatus. Thus in oneportion, usually at a point removed from the agitator or impeller,velocities would be much slower than close to it. However, the rate ofoperation of such a plant is determined by the maximurn velocity foundtherein, so that reducing these maximum velocities to an operatingvalue, reduced velocities at other points to ineiiicient levels. I havefound that by interposing the pressure chamber between the hood and theflow passage, 1 am able to distribute the flows more evenly throughoutthe volume of the hood and throughout the length oi the passagewaydischarging over it. This results in more uniform flows in all parts ofthe treating basin and raises the operating efilciency of the plant as awhole.

When applied to a shallow treating basin, the intermediate pressurechamber permits a recycling of a much larger proportion of the slurryunder the hood, thereby permitting a slower and less turbulent flowthrough the passageway and over the hood, with the result that the outerspace is more quiescent and the slurry interiace between slurry andclear water in the quiescent section is more stable. This permitsreducing by a considerable amount the depth or clear water above theslurry interface.

When considered as an apparatus my invention comprises a treating basinwith the usual inlet and outlet, a hood in the lower part oi the basin,a passageway leading from the top of the space enclosed by the hood anddischarging over the hood, 'mlpelling means for causing recirculation ofmaterial under the hood and a flow throueh the passageway, a partitionso constructed and arranged in relation to the hood and to the inapelleras to form a pressure chamber between the hood and the passageway, and.outlet open= ings, preferably valved, discharging from the pressurechamber into the passageway and also directly back into a lower portionof the space enclosed by the hood for return of liquid from the pressurechamber thereto. When considered as a process my invention comprises animprovement over the conventional slurry treating process wherein liquidto be treated and chemical treating reagents are mixed in and with aslurry containing solids separated from previously treated liquid, in amixing zone, and a portion of such slurry is passed from the mixing zonethrough a relatively quiescent slurry holding space and back into themixing zone, clear liquid escaping from the upper surface oi the slurryin the slurry holding space. I add to the conventional slurry processthe step of pumping slurry from the mixing zone into a pressure chamberand directing part 01' the flow from the pressure chamber over the hoodand directing another and major portion back into the mixing zone in amanner to insure proper distribution and direction of the return flowwhereby mixing is secured or aided, and controlling the actual andrelative volume of the two such flows.

My invention will be more readily understood from the drawings anddescription which follow:

Figure 1 is a vertical, longitudinal crosssectlonal view of a preferredembodiment of my invention.

Figure 2 is a transverse, vertical cross-sectional view of the apparatusshown in Figure 1;or in a round or square tank, a diametrical verticalcrosssectional view of a preferred form of my inventlon.

Figure 3 is a transverse, vertical cross-sectional view of a modifiedform or apparatus.

Figure 4 is a cross-sectional view of the distribution arms shown inFigure 3.

In order to more completely describe my invention I have shown it asapplied to a rectangular, or oblong, treating basin although it will beobvious to those skilled in the art that it can also be applied. toround or square treating tanks. Thus I show a tank It! formed by endwalls H and I2, respectively, side walls 43 and i4, respectively, and afloor I5. Preferably the basin ID will be provided with a valved drainl6 and an integral fill l'l between the side walls and floor of thebasin as shown. The tank I9 is also provided with a launder l8,separated from the tank proper by a weir l9, and discharging intoefliuent conduit 20. In an oblong treating basin it is usuallyadvantageous, to provide a launder I8 along each side wall, l3 and 14respectively, so that treated water can be taken from each side of thebasin. Preferably, the basin it is also provided with one or more sludgeconcentrators ill from which leads a sludge discharge line 22. Thesludge concentrators 2!, as is now known in the art, are open-toppockets. The sludge concentrators 2| are placed at a suitable elevationon the side walls, and in a rectangular basin there should be one ormore such concentrators on each side wall 53 or it.

In a rectangular treating basin, the arrangemerit of parts willpreferably be symmetrical on both sides of the axis of the basin, and ina circular tank, the arrangement of parts will be as near aspracticable, symmetrical about the center. For this reason duplicateparts, one on each side of the axis (as in Figure 2), will be given onlyone reference character.

In the basin it I place a hood 353 which in an belong basin wouldpreferably be formed by slopirig plates 3|. At the lower ad of theplates 38 preferably are placed vertical skirts 32. The hood structureis supported by any suitable means such as legs 33. The hood 33 will, atany elevation, preferably have a shape corresponding to that oi thebasin, i. e. will be rectangular in a rectan ular basin or circular in acircular basin. As is well known in the art the hood 3G is spaced abovethe floor of the tank so as to provide a continuous slot 34 below thehood to afford communication from the outer portion of the tank into thelower portion of the space confined by the hood. A passageway 35 leadsfrom the top ond pair of vertical walls, or partitions, 31 extendingfrom above the liquid level to a level adjacent that of the top of theplates 3 I, and spaced a suitable distance from the inner walls 36. Thusthe passageway 35 leads from the upper portion of the space enclosed bythe hood 3!! upwardly inside the inner vertical walls 36 and thendownwardly between the parallel walls 36 and 31, discharging (in Figures1 and 2) through the outlets 38 over the top of the plates 3|.Preferably I provide a plurality of stilling bafiles 39 between theparallel walls 36 and 31 so as to eliminate as much as possibletangential, or diagonal, flows which might upset Operation of the plant.In an elongated basin the sloping plates II and the partition walls 36and 31 may extend substantially the length of the basin, in which casethe hood 30 and passageway 35 may be closed by a solid partition 52,asshown in Figure 1.

For purposes of my invention lt-is desirable that the hood 30 beprovided with a relatively flat top such as is provided by ahorizontalplate 40 leavinga central communication 4| between the top ofthe hood and the passageway 35. A l

a central inlet opening 5|, as hereafter described.

The floor 42 is spaced a short distance from the sloping walls 3| so asto provide relatively narrow slots 43 between the space above the floor.42 and the lower part of the hood. At the slots 43, I

provide a plurality of flow directing baflies 44 perpendicular to thesloping walls 3|oi the hood, so that flows issuing from the space Aabove the floor 42, which for convenience will be called the pressurechamber, will be normal to that surface and not diagonal. I have foundthat diag onal flows in a rectangular basin tend to strike the surfaceof the fill at an angle'and deflect upwardly outside the hood, thuscausing .boils in the outer chamber. The directing baflles 44 preventsuch action and therefore tend to make'the. 3Q

apparatus more emcient.

In most sizes of oblong basins a single propeller will be suflicient tosecure the desired circulation,

although in those which are relatively longer than ordinary, two or moremay be desirable. I

' slots 4| and 43,. a greater or lesser proportion of Thus in thefigures I show a single propeller 45 placed at the intersection of thelongitudinal and transverse axis of the basin. The propeller 45 ismounted on a suitable shaft 46 driven by a motor 41 through a speedreducer 48. The shaft 45 preferably is journaled in a suitable bearing49 at its lower end, as shown. Surrounding the propeller is acylindrical wall 50, forming a passageway 5| which afiords communicationfrom the mixing chamber B to the pressure chamber 45 A. When thepropeller 45 is driven at a suitable speed, liquid is pumped from thelower part of the hood into the pressure chamber A, from where it isdistributed through the slot 4| leading to the passageway 35 and theslots 43 leading 50 back to the mixing chamber B in the lower part ofthe space enclosed by the hood.

In many installations it is possible to predetermine the relative areasof the slots 4| and 43 so as to provide a predetermined relation betweenthe flow through the upper passageway 35 and that back to the space B inthe lower part of the hood. However, in some instances it is desirableto provide means for varying the size of one or both, so as to vary theproportion of these .flows 0 as operating conditions demand. Thus I showa pair of horizontal valve plates adjustable to vary the width of theslot 4|. For purposes of illustration the plates 60 are shown as restingupon the roof 40 of the pressure chamber A, and

as adjustable through the medium of bell cranks GI and adjusting rods52. Likewise the lower slots 43 are shown as equipped with adjustablevalve plates. 63 which can be adjusted to their proper position throughthe medium ofhell cranks 64 and adjusting rods 55. Thus the relativeareas of the slots or passageways 4| and 43 can be adjusted from time totime as may be necessary or expedient, such as by change in thecharacter of the liquid being treated or the like. 15

It should be obvious that in many, if not most, instances it will not benecessary to provide both the passageway 35 and the slots 43 with avalve means, for varying the size of the orifice in either 5 willautomatically vary the amount and velocity I 1 tank. Thus, in arectangular basin, it is preferred that raw water be introduced throughlongitudinal conduits Ill beneath and adjacent the outer 1 side of thefloor 42 of the pressure chamber as shown. These inlets communicate withrawv water lines ll. Each of the inlets is provided with a I small slot.I2 .discharging parallel to the flow through the slots 43 from thepressure chamber Ainto the lower space or mixing chamber B. The

treating reagent is introduced through chemical feed line 13 which candischarge into the raw water line 1| orinto the space below the hood,

as shown. 1

It wm be seen that the horizontal floor 4|.

divides thev space under the hood into a. pressure chamber A above thefloorand a" primary mixing zone .3 below it. Rotation of the propeller45 causes liquid to be pumped from the lower space B into the upperspace A. As the slots 4| and 43 are somewhat restricted pressure will bebuilt up in'the pressure chamber A to cause flow upwardly'through theslot 4| and passageway 35 which discharges downwardly over the hood 30,

and another fiow outwardly through slots 43 inside the hood. Accordingto the width of the the total flow will pass through them. Ordinarily itis preferred that a minor portion pass through under the hood forfurther inixingand reaction with slurry, water and chemical. Theoperation of the'apparatus of my inven tion will be readily apparent. Ingeneral the operation of myv apparatus is similar to that ofconventional "Accelators. of the propeller 45 liquid is pumped from thelower mixing chamber B into the pressure chamber A. It is assumed thatthe pumping capacity of the propeller 45 will be in excess of the volumeof liquid that will pass through the upper slot 4| into passageway 35and that the slots 43 will be restricted, as by moving the valve plates43 toward a closed position, so as to create a, higher pressure in thepressure chamber A. This higher pressure will naturally cause a flow ofthe balance of the pumping capacity through the slots 43 directly backinto the mixing zone B. Thus I deliberately create in the chamber A avolume of liquid which is subjected to pressure greater than that foundin other parts of the basin. This results in a uniform flow through theupper slot 4| into the passageway 35 throughout its entire length,resulting in a uniform flowover the entire area of the hood. The excesspressure in the pressure zone A also causes a uniform flow of liquidHowever, on operation I am enabled to cause uniform operating conditionsthroughout an oblong tank of considerable lengtlnand thus secureunifomireatlag'm thewhole volume of the basin. Unless the tank isexceptionally long I have found that a single liquid moving member, suchas a propeller 48, is suflicient to provide proper operation. In fact asingle large propeller gives better results than a plurality of smallerones, as in apparatus of the usual design flows from two or morepropellers or other liquid moving members conflict, often resulting inthe deposit of sludge in various parts of the basin.

I have found in some installations, and particularly those in which thedepth of clear liquid in the upper part of the basin is relativelyshallow, that it is expedient to provide means for positivelydistributing the flow of slurry throughout the cross-sectional area ofthe quiescent chamber. When the width of the basin is relatively' greatin relation to its depth, I have found that the discharge of slurrythrough the passageway 35 and its lower open end 88 downwardly over thehood 3| does not utilize the full width of the clarification basin toits best advantage. In such types of apparatus I prefer to provide aplurality of distributing arms such as are shown in Figure 3. The basinand the partition structure which form the hood, and the two separatechambers under the hood are essentially the same as in Figure 2 and neednot be described. In this form, the passageway 35 is replaced by aplurality of flow distribution arms. In this embodiment vertical wallsso rise from the top of theslopingwalls II to above the liquid level inthe basin. In the embodiment shown in Figure 3, the pressure chamber hasno roof but is open to the atmosphere so that it is necessary that theconfining walls 80 rise substantially above the liquid level to preventflow over such walls, as the operation of the propeller 45 will causethe liquid level in the pressure chamber to be considerably higher thanelsewhere in the basin. Extendin laterally from the vertical wall 88 areflow distributing arms 8i. One of these arms is shown in crosssection inFigure 4. The distributing arm comprises a substantially square trough82 mounted so that the diagonals between corners constitute the verticaland horizontal axes. The top corner is cut oif to provide a, slot 83 asshown. Mounted above the slot 83, by any suitable means such as j risers84 is a V-shaped hood 85. The hood 85 is designed as to direct flowissuing upwardly I through the slot 83 horizontally and slightly gdown'wardly from the trough 8|. I also prefer -=i-'to place a pluralityof orifices or a slot 86 at theibottom corner of the trough as shown.These oriiices or lower slots, either form being suit- .able, serve thedouble purpose of preventing deposit of solids in the trough itself andalso of preventing the deposit of solids on the hood 3| underneath theslots, as without such downwardly discharging orifices there might besuflicient quiescence underneath the trough to permit such deposit. Inthe embodiment illustrated it is obvious there is no separate flowpassage between the pressure chamber A and the flow distribution arms8|, so that I prefer to provide each arm with a gate valve 81 operatedby an extension rod 88, as shown in the right-hand arm of Figure 3. Bythis means the flow througheach arm can be accurately controlled. Itwill be obvious that a similar result could be secured by interposing aflow passage, such as 35, shown in Figure 2, between the high pressurechamber A and the plurality of how arms 8!. In that case the valvecontrolling the opening between the pressure chamber A and he flowpassage would be sumcient to control the flow through the arms with- Iout the necessity of .the individual valve in each arm.

Operation of the embodiment shown in Figure 3 is similar to that ofFigures 1 and 2. The impeller 45 pumps a large amount of slurry from 10the lower mixing chamber B into the pressure chamber A, whichin thisinstance extends to the top of the tank. From pressure chamber A slurryflows through the plurality of distribution arms from which it isdistributed in a thin sheet immediately subjacent the slurr interface inthe outer clarification space. Such an apparatus provides for a uniformdistribution of slurry throughout the outer clarification space, andassists in uniform operation of all portions of the apparatus.

It will be obvious that the apparatus of my invention can take severalforms. For example it can be applied with considerable value to round orsquare tanks, in which case Figure 2 would represent a vertical viewtaken along the diameter of the tank. It is obvious that the form of thepressure chamber can vary over a considerable range as the particularform of this chamber is not critical. In fact it could be placed in thespace enclosed by the inner vertical walls 36. It is necessary, however,that there be a passageway from the pressure zone leading to the,quiescent zone (discharging over the hood) and another passageway 43,leading a large portion of the flow from the liquid impeller directlyback to the mixing chamber B. As indicated above, these passagewayspreferably are provided with means to adjust flows therethrough, so asto control the volumes and velocities of the flows in the various partsof the basin.

I claim:

1. Liquid treating apparatus comprising a tank,

, 8. treated liquid outlet from the upper part of the tank, a partitionstructure forming a, hood in the 5 lower part of the tank, a secondpartition inside the hood and dividing the space inside the hood into anupper pressure chamber and a lower mixing chamber, a passageway openingfrom the pressure chamber and discharging downwardly over the upper sideof the hood, a passageway opening from the pressure chamber to themixing chamber and located inside and adjacent the sides of the hood, apassageway leading from the mixing chamber to the pressure chamber, amechanically driven liquid moving member so positioned and of such acapacity as to pump a volume of liquid through said last mentionedpassageway from the chamber into the pressure chamber in excess of thecapacity of said passageway leading do from said pressure chamber, fordischarge through said second mentioned passageway into said mixingchamber, to establish a circulation throughout, and to mix the contentsof, said mixing chamber, liquid inlet means for delivering liquid as tobe treated and a'treating reagent to said mixing chamber, and a solidsoutlet from the lower part of said tank.

2. Liquid treating apparatus comprising a basin, a treated liquid outletfrom the upper portion of said basin, a solids outlet from a lowerportion of said basin, a partition structur forming in said basin amixing chamber in the lower part ofthe basin and a pressure chamber inthe central portion of the basin superposed over said to mixing chamber,a passageway leading from the chamber and discharging downwardly oversaid partition structure, an inlet iromsaid chamber into said pressurechamber, inlet means in th lower part of said basin so constructed andarranged as to deliver liquid to be treated and a treating reagentv tosaid mixing chamber, a return passageway leading from the pressurechamber to the mixing chamber adjacent the sides thereof, said pumpingmember being of such a capacity as to pump a volume of liquid in excessof the capacity of said first mentioned passageway for discharge throughsaid return passageway into said mixing chamber, to establish acirculation in, and mix the contents oi, saidmixing 'ehamber and valvemeans for controlling through each of said passageways.

3. Liquid treating apparatus comprising a basin, a treated liquid outletfrom the upper portion of said basin, a solids outlet from a lowerportion of said basin, a partition structure forming in said basin amixing chamber in the lower part of the basin and a pressure chamber inthe central portion 01 the basin superposed over said mixing chamber,and a laterally adjacent quiescent chamber and three passageways, onebetween the quiescent chamber and the mixing chamber adjacent the floorof the basin, the second leading from the pressure chamber anddischarging into an intermediate level of the quiescent chamber, and thethird leading from the pressure chamber and discharging into the mixingchamber, inlet means in the lower part 01' said basin so constructed andarranged as to deliver liquid to be treated and a treating reagent tosaid mixing chamber, an inlet from said mixing chamber into saidpressure chamber, a power driven pumping member so positioned as tocause flow through said inlet and of such a capacity as to pump a volumeof liquid in excess of the capacity of said second passageway, throughsaid inlet for discharge through said third passageway, to establish acirculation in, and mix the contents of, said mixing chamber, and valvemeans for controlling flows through said second and third passageways.

4. In a liquid treating apparatus comprising a basin, a treated liquidoutlet from the upper part ofsaid basin, a sloping wall structureforming a centrally located hood in the lower part of said basin, apassageway leading from the upper POI-f tion of said hood anddischarging over said sloping wall structure, means adapted to mix thecontents under said hood and to cause a flow through said passageway, asolids outlet from the lower part of said basin, and inlet means forintroducing'liquid to. be treated and a treating reagent under saidhood, the combination 'of a partition structure forming a pressurechamber in the upper portion of the space enclosed by said hood, aninlet into said pressure chamber from the lower portion of the spaceenclosed by said hood, and an outlet from said pressure chamber to thelower portion of the space enclosed by said hood.

5. .A liquid treating apparatus comprising a basin, 9, treated liquidoutlet in the upper part of said basin, 3. solids outlet from the lowerpart of said basin, a wall structure forming a centrally located hood inthe lower part of said basin and a quiescent chamber in the upper partof said basin, inlet means in the lower portion of said basin soconstructed and arranged as to deliver liquid to be treated and atreating reagent to said hood, a passageway leading from the upper flow7 10 portion or said hood and discharging downwardly over said hood, anda power driven impeller adapted to mix the contents of said hood and tocause a flow through said passageway, characterized by a secondpartition structure forming a pressure chamber in the upper .portion ofsaid hood and a mixing chamber in the lower portion thereof, an inletassociated with said impeller and affording communication into saidpressure chamber from said mixing chamber, and outlets from saidpressure chamber into the mixing chamber.

6. In a liquid treating apparatus including a basin, a treated liquidoutlet in the upper part of said basin, a solids outlet from a lowerportion of said basin, a centrally located partition structure in thelower part of said basin forming an enclosed mixing chamber and an upperquiescent chamber, inlet means in the lower portion of said basin soconstructed and arranged as to deliver liquid to be treated and atreating reagent to said mixing chamber, a passageway leading from theupper portion of the space enclosed by said partition structure anddischarging outwardly on the outside 01 such structure, and a powerdriven impeller adapted to mix the contents of said mixing chamber andto cause a flow through said passageway, the improvement which comprisesa second partition structure forming a pressure chamber interposedbetween said mixing chamber and said passageway, an inlet from themixing chamber into said pressure chamber, an outlet from said pressurechamber to said passageway, a flow passage from said pressure chamberinto the mixing chamber, and means for controlling the relative volumesof the flows from said pressure chamber through said passageway and saidflow passage, respectively. I

'7. Liquid treating apparatus comprising an elongated tank, a partitionstructure forming an elongated hood in the lower part of the tank spacedabove the floor thereof, an outlet from the top of said hood, a secondpartition means forming a passageway leading from said outlet anddischarging downwardly above the hood on each side thereof, a thirdpartition forming a pressure chamber in the upper part of the hood, areturn passageway leading from the pressure chamber to the lower portionof the space enclosed by the hood and located adjacent the sides of thehood, an inlet into said pressure chamber from the lower portion 01' thespace enclosed by the hood, a power-driven liquid moving member sopositioned as to pump liquid through said inlet into the pressurechamber, a treated liquid outlet from the upper part of the tank, aliquid inlet discharging under-the hood and a solids outlet from a lowerportion of the tank.

8. Liquid treating apparatus comprising a basin, a treated liquid outletfrom the upper portion of said basin, a solids outlet from a lowerportion of said basin, means forming in said basin a mixing chamber inthe lower part of the basin, a pressure chamber in the central portionof the basin superposed over said mixing chamber and a laterallyadjacent quiescent chamber, inlet means into the lower portion of saidbasin so constructed and arranged as to deliver liquid to betreated anda treating reagent to the mixing chamber, a passageway from the pressurechamber discharging outwardly in said quiescent chamber, an inlet fromsaid mixing chamber to said pressure chamber, pumping means sopositioned in relation to said inlet as to cause flow from said mixingchamber into said pressure chamber, a return passageway from thepressure chamber to the mixing chamber, and means for controlling flowthrough each 01' said passageways.

9. Liquid treating apparatus comprising a basin, a treated liquid outletfrom the upper portion of said basin, an inlet into the lower portion ofsaid basin, a solids outlet from a lower portion of said basin, apartition structure forming in said basin a mixing chamber in the lowerpart of the basin, a pressure chamber in the central portion of thebasin superposed over said mixing chamber and laterally extendingquiescent chamber, an inlet opening from the lower part of the quiescentchamber into said mixing chamber, an inlet opening from the mixingchamber into the pressure chamber, a power driven pumping memher sopositioned as to cause flow through said last mentioned inlet opening,horizontally extending fiow arms leading from said pressure chamberacross an intermediate elevation of th quiescent chamber, orifices insaid flow arms, a passageway leading from the pressure chamber anddischarging into the mixing chamber, and valve means for controllingfiows through said flow arms.

10. A process for treating water which comprises maintaining a body ofslurr containing solids accumulated from previously treated water,mixing such slurry, water to be treated, and a treating reagent in aconfined mixing zone in the lower portion of said body of slurry to formadditional slurry, continuously pumping slurry from said mixing zoneinto a pressure zone in an upper portion of said body of slurry, passingone portion of the slurry from the pressure zone laterally below theupper surface of the unconfined portion of the body of slurry and thenceback into the confined mixing zone, and passing another portion of theslurry from the pressure zone directly back into the confined mixingzone, exuding clarified water from th upper surface of the unconfinedportion of the slurry into a clear water space and then withdrawing theclear water from the upper part of said clear water space, andwithdrawing excess solids from said body of slurry.

11. In a process for treating water wherein water to be treated and areagent are mixed in and with a slurry of water undergoing treatment andsolid particles accumulated from previously treated water in a confinedmixing zone and a predetermined portion of the slurry in the mixing zoneis discharged from the mixing zon and passed into a lower portion oi aquiescent clarification zone, clarified water being displaced from theupper surface of the slurry in the quiescent zone into a clear waterspace in the upper portion of said quiescent zone and thereafter fromthe upper part .,o;; said quiescent zone, and a portion of suchdncl'i'arged slurry is returned to the mixing zone, the improvementwhich comprises pumping a quantity of slurry inexcess of saidpredetermined portion from the mixing zone into an intermediate pressurezone, passing the Pre- 12 determined portion 01 the slurry into saidclarification zone from such pressure zone, and retuming the excessportion directly to the mixing zone.

12. A process for treating water which comprises maintaining a body ofwater undergoing treatment, dividing said body of water into a confinedmixing zone in the lower portion of said body of water, a superposedpressure zone and a leterally adjacent quiescent zone, mixing water tobe treated, slurry containing particles collected from previouslytreated water and a treating reagent in the confined. mixing zone toform additional slurry, pumping said slurry into the pressure zone,passing a portion of the slurry in the pressure zone outwardly across anintermediate level of the quiescent zone and passing another portion ofthe slurr in the pressure zone directly back into the confined mixingzone, returning a portion of slurry from the lower level of the quies-'cent zone into the confined mixing zone, with, drawing clarified waterfrom the slurry in the quiescent zone upwardly into a clear water spaceand thence from the clear water space, and withdrawing excess solidsfrom said body of slurry.

13. Liquid treating apparatus comprising an elongated tank, alongitudinal partition structure forming an elongated mixing spacearranged longitudinally in the lower part 01' the tank, means includinga power driven pumping member forming a zone of increased pressure at alevel above said mixing space, a passageway leading from the upper partof said pressure zone and discharging outwardly in said tank outside ofsaid space and said zone at a level substantially below the top of saidtank, a passageway, for returning a portion of the liquid in thepressure zone directly to the mixing space, said pumping member havingsuch a capacity as to pump a volume oi liquid in excess of the capacityof the passageway from the upper part of said pressure zone, fordischarge through said return passageway from said pressure zone to saidmixing space, to establish a circulation in, and mix the contents of,said mixing space, a treated liquid outlet from the upper part of thetank, means for delivering liquid to be treated to the mixing space,means for delivering treating reagent to the liquid to be treated, and asolids outlet from a lower portion of the tank. I

WALTER H. GREEN.

REFERENCES CITED The following'references are of record in the file ofthis patent:

UNITED STATES PATENTS

